Patent GB-622496-A (GB)
Title: Improvements in photographic cameras
IPC: G03B7/12
Filed: 1946-10-24
Abstract: 622,496. Photographic cameras. WATSON & SONS, Ltd., W., and FRY, C. H. Oct. 24, 1946, No. 31646. [Class 98 (i)] [Also in Group XL (b)] A camera incorporates a photo-electric cell which actuates a galvanometer pointer which is displaceable out of its plane of movement to depress one of a number of stops to limit the travel of an arm determining the time of exposure or the aperture. General description.-The invention is described with reference to a roll-film camera in which the aperture is selected by the user and the time of exposure is automatically controlled by a photo-electric cell. The cell receives light through louvres 19, Fig. 1, which are adjusted in accordance with the aperture by levers 20, 21 and displaceable cam 22; for long or " time " exposures, shutters 25 are opened to admit more light, while for short or " instantaneous " exposure, shutters 25 are closed to reduce the light reaching the cell. The cell actuates a galvanometer whose pointer 28, Fig. 2, moves over a series of depressible stops 29, 30, stops 29 corresponding to short exposures, and stops 30 corresponding to long exposures; a presser bar 39 actuated by depression of button 44 over levers 43, 42, presses pointer 28 downwards to engage one of the stops 29, 30 and move it into a position to limit the movement of one of the rotatable arms 37, 38, the first of which determines the extent to which a focal plane shutter shall be opened, and the second of which determines how long the shutter shall remain fully opened. Short exposures.-The shutter 25 is closed so that the galvanometer pointer 28 moves over stops 29 only; button 44, Fig. 2, is depressed to lower the presser bar 39 and lift latch 57, thus allowing spring 54 to actuate levers 52, 51, 48 and gears 46, 45 to move arm 37 until it is arrested by the depressed stop. Lever 51 carries a rack engaging a pinion 55 which is thus rotated and positions a face-cam 93, Fig. 5, in accordance with the stop depressed by pointer 28. Button 44, Fig. 2, is then pushed inwards, rocking lever 88 to free latch 84 and allow spindle 56, Fig. 5, to rotate under the action of spring roller 13 until cam 94 engages cam 93, thus allowing blind 11 to be opened to an extent determined by the depressed stop. When cams 94, 93 meet, pinion 55 is forced upwards to lift latch 91 and allow the closing blind 12 to be drawn across the exposure area 100 by the spring roller 83; blind 12 will thus follow blind 11 with a slit 101 determined by the position of the pointer 28. Long exposures.-The cell is exposed to more light by opening shutter 25 so that the pointer 28 is positioned over one of the stops 30. On depression of button 44, arm 37 moves its full distance and blind 11 is entirely withdrawn. At the limit of its movement, arm 37 releases arm 38 which moves under the action of a spring 72 acting over a rotatable clockwork carriage 65 and levers 64, 62, 61 until it reaches the stop 39 depressed by the pointer 28. A lover 68 mounted eccentrically on the clockwork driving wheel 67 is thus moved to the right to an extent determined by the depressed stop. When pinion 55, Fig. 5, is forced upwards as described for short exposures and latch 91 is lifted, finger 92, Fig. 5, engages with stop 69 on lever 68 and under the pull of the spring roller 83 forces arm 68 to the right until arm 68 rides over pin 74 to lift stop 69 free of finger 92, thus allowing the closing blind 12 to be drawn across the exposure area 101 by spring roller 83. The time between the withdrawal of blind 11 and the drawing of blind 12 is thus determined by the time required to press lever 68 to the right against the clockwork driving wheel 67, the clockwork carriage 65 being held stationary by arm 38. Re-setting.-A lever 102 is operated and through gear 103, pinion 104 and gears 105 ... 108 rewinds the closing blind and unwinds the opening blind in an overlapping relation as well as advancing the film; a pin 109 on pinion 104 engages arm 53 of bell-crank lever 52 to rotate it to re-set arm 37; arm 38 is re-set by the engagement between a skirt on gear 45 and the skirt carrying arm 38.